Recovery of aliphatic hydrocarbons

ABSTRACT

The invention relates to a process for the recovery of aliphatic hydrocarbons from a liquid stream comprising aliphatic hydrocarbons, heteroatom containing organic compounds and optionally aromatic hydrocarbons, involving a) liquid-liquid extraction of said liquid stream with an extraction solvent; b) mixing the extract stream, comprising extraction solvent, heteroatom containing organic compounds and optionally aromatic hydrocarbons, with a demixing solvent to remove part of the heteroatom containing organic compounds and optional aromatic hydrocarbons; and c) separation of the remaining stream into a demixing solvent stream and an extraction solvent stream, wherein before and/or after step c) additional heteroatom containing organic compounds and optional aromatic hydrocarbons are removed from that remaining stream and/or from a stream resulting from step c), respectively, by contacting the latter stream (s) with a sorption agent. Further, the invention relates to a process for the recovery of aliphatic hydrocarbons from plastics comprising the above-mentioned process; and to a process for steam cracking a hydrocarbon feed comprising aliphatic hydrocarbons as recovered in one of the above-mentioned processes.

FIELD OF THE INVENTION

The present invention relates to a process for the recovery of aliphatichydrocarbons from a liquid hydrocarbon feedstock stream comprisingaliphatic hydrocarbons, heteroatom containing organic compounds andoptionally aromatic hydrocarbons; to a process for the recovery ofaliphatic hydrocarbons from plastics comprising the above-mentionedprocess; and to a process for steam cracking a hydrocarbon feedcomprising aliphatic hydrocarbons as recovered in one of theabove-mentioned processes.

BACKGROUND OF THE INVENTION

Waste plastics can be converted via cracking of the plastics, forexample by pyrolysis, to high-value chemicals, including olefins andaromatic hydrocarbons. Pyrolysis of plastics can yield product streamscontaining hydrocarbons in a wide boiling range. Hydrocarbons from suchpyrolysis product streams can be further cracked in a steam cracker toproduce high-value chemicals, including ethylene and propylene which aremonomers that can be used in making new plastics.

WO2018069794 discloses a process for producing olefins and aromatichydrocarbons from plastics wherein a liquid pyrolysis product stream isseparated into a first fraction having a boiling point <300° C. and asecond fraction having a boiling point 300° C. Only said first fractionis fed to a liquid steam cracker, whereas said second fraction isrecycled to the pyrolysis unit. In the process shown in FIG. 1 ofWO2018069794, said separation is performed in a hydrocarbon liquiddistillation unit. Having to separate the liquid pyrolysis productstream into two fractions is cumbersome (e.g. energy intensive). Afurther disadvantage is that the heavier portion of the liquid pyrolysisproduct stream has to be sent back to the pyrolysis unit for a deeperpyrolysis. This results in yield loss through the formation of gas andan increasing amount of solid side-product (coke) which is eventuallynot sent to the steam cracker. In one embodiment of the process ofabove-mentioned WO2018069794 (see FIG. 2 ), the first fraction having aboiling point <300° C. is first conveyed together with hydrogen to ahydroprocessing unit to produce a treated hydrocarbon liquid streamwhich is then fed to the liquid steam cracker. Such hydroprocessing isalso cumbersome, as it is capital intensive and requires the use ofexpensive hydrogen (H₂).

Further, US20180355256 discloses a method for deriving fuel fromplastics, the method comprising subjecting a quantity of plastics to apyrolytic process, thereby to convert at least part of the plastics to acrude fuel; and extracting the fuel in a directly usable form by wayof: 1) a first extraction step comprising counterflow liquid-liquidextraction using one or more extraction solvents to extract one or moreimpurities from the crude fuel; and 2) a second extraction stepcomprising counterflow extraction of resultant contaminated extractionsolvent(s) from the first extraction step. In the process as shown inFIG. 2 of US20180355256, a crude fuel (i.e. a crude diesel) that is madeby pyrolysis of plastics, is first subjected to extraction withN-methyl-2-pyrrolidone (NMP) to extract one or more impurities,including sulfur compounds and aromatics, from the crude fuel. Thecontaminated NMP from the first extraction step is then subjected to asecond extraction step using water, to increase the polarity of thecontaminated extraction solvent, thereby separating off said impurities.In a final step, the water-contaminated NMP from the second extractionstep is distilled using a standard distillation column, which gives riseto recycle water and recycle NMP.

The feed to the distillation column as disclosed in above-mentionedUS20180355256 (FIG. 2 ) may still comprise a certain amount ofheteroatom containing organic contaminants and aromatic contaminants.Said distillation may result in that part of said contaminants isseparated off together with the recycle water because water and suchcontaminants may form an azeotrope, thereby reducing the quality of thewater recycle stream. In case that recycle water is recycled to thecolumn used in the second extraction step, the concentration of thesecontaminants in the recycle water will increase in what is denominated“build-up”, in addition to a build-up of these contaminants in therecycle NMP to be used in the first extraction step. This can result ina lower efficiency of the first and second extraction steps.US20180355256 concerns a method for deriving fuel from plastics. Suchbuild-up of these contaminants (in said recycle NMP) may result in thatthe cleaned oil still comprises a relatively high amount of thesecontaminants, which is of particular concern when such cleaned oil wouldbe fed to a steam cracker, instead of being used as a fuel, because ofthe negative impact of these contaminants on the yield, selectivity andreliability of steam crackers.

There is an ongoing need to develop improved processes for the recoveryof aliphatic hydrocarbons from liquid streams comprising aliphatichydrocarbons, heteroatom containing organic compounds and optionallyaromatic hydrocarbons which may originate from cracking waste plastics,in specific mixed waste plastics, especially before feeding suchrecovered aliphatic hydrocarbons to a steam cracker. It is an object ofthe present invention to provide such process for the recovery ofaliphatic hydrocarbons from such liquid streams, which process istechnically advantageous, efficient and affordable, in particular aprocess which does not have one or more of the above-mentioneddisadvantages, as discussed above in connection with WO2018069794 andUS20180355256. Such technically advantageous process would preferablyresult in a relatively low energy demand and/or relatively low capitalexpenditure.

SUMMARY OF THE INVENTION

Surprisingly it was found by the present inventors that such process canbe provided by a) liquid-liquid extraction of a liquid stream whichcomprises aliphatic hydrocarbons, heteroatom containing organiccompounds and optionally aromatic hydrocarbons, with an extractionsolvent a) which contains one or more heteroatoms; b) mixing a streamresulting from step a) which comprises extraction solvent a), heteroatomcontaining organic compounds and optionally aromatic hydrocarbons, witha demixing solvent b) to remove part of the heteroatom containingorganic compounds and optional aromatic hydrocarbons, wherein demixingsolvent b) contains one or more heteroatoms and has a miscibility inheptane which is lower than the miscibility of extraction solvent a) inheptane; and c) separation of at least part of a stream resulting fromstep b), which comprises extraction solvent a), demixing solvent b),heteroatom containing organic compounds and optionally aromatichydrocarbons, into a demixing solvent b) containing stream and anextraction solvent a) containing stream, wherein (i) before step c) atleast part of said stream resulting from step b) is contacted with asorption agent (or sorbent); and/or (ii) after step c) at least part ofa stream resulting from step c), which comprises demixing solvent b),heteroatom containing organic compounds and optionally aromatichydrocarbons, is contacted with a sorption agent (or sorbent), whereinsaid sorption agent removes at least part of the heteroatom containingorganic compounds and optional aromatic hydrocarbons from the latterstream(s).

Accordingly, the present invention relates to a process for the recoveryof aliphatic hydrocarbons from a liquid hydrocarbon feedstock streamcomprising aliphatic hydrocarbons, heteroatom containing organiccompounds and optionally aromatic hydrocarbons, said process comprisingthe steps of:

-   -   a) contacting at least part of the liquid hydrocarbon feedstock        stream with an extraction solvent a) which contains one or more        heteroatoms and subjecting the liquid hydrocarbon feedstock        stream to liquid-liquid extraction with the extraction solvent        a), resulting in a first stream comprising aliphatic        hydrocarbons and a second stream comprising extraction solvent        a), heteroatom containing organic compounds and optionally        aromatic hydrocarbons;    -   b) mixing at least part of the second stream resulting from        step a) with a demixing solvent b) which contains one or more        heteroatoms and has a miscibility in heptane which is lower than        the miscibility of extraction solvent a) in heptane, and        separating the resulting mixture into a first stream comprising        heteroatom containing organic compounds and optionally aromatic        hydrocarbons and a second stream comprising extraction solvent        a), demixing solvent b), heteroatom containing organic compounds        and optionally aromatic hydrocarbons;    -   c) separating at least part of the second stream resulting from        step b) into a first stream comprising demixing solvent b),        optionally heteroatom containing organic compounds and        optionally aromatic hydrocarbons and a second stream comprising        extraction solvent a);    -   d) recycling at least part of the extraction solvent a) from the        second stream resulting from step c) to step a); and    -   e) optionally recycling at least part of the demixing solvent b)        from the first stream resulting from step c) to step b),    -   wherein:    -   (i) before step c), heteroatom containing organic compounds and        optionally aromatic hydrocarbons are removed from the second        stream resulting from step b) by contacting at least part of        that stream with a sorption agent; and/or    -   (ii) after step c), heteroatom containing organic compounds and        optionally aromatic hydrocarbons are removed from the first        stream resulting from step c), wherein that stream comprises        demixing solvent b), heteroatom containing organic compounds and        optionally aromatic hydrocarbons, by contacting at least part of        that stream with a sorption agent.

Advantageously, in the present invention, there is no need forhydrotreating (treatment with H₂) because of said liquid-liquidextraction in step a). Furthermore, advantageously, a liquid hydrocarbonstream having a wide boiling range, such as plastics pyrolysis oil, maybe treated in the present process with a relatively low yield loss andfeed degradation. This implies that the costs of a hydrocarbon feed to asteam cracker may be reduced considerably by applying the presentinvention.

Further, heteroatom containing organic compounds and any aromatichydrocarbons may eventually partition into the stream comprisingextraction solvent a) and demixing solvent b) resulting from step b) ofthe present process. Said heteroatom containing organic compounds andaromatic compounds may comprise the components with the highest polarityof all the heteroatom containing organic compounds and aromaticcompounds as extracted in step a) of the present process. In such case,advantageously, by the sorption step(s) in the process of the presentinvention, relatively pure demixing solvent b) recycle and relativelypure extraction solvent a) recycle streams, that are substantially freeof heteroatom containing organic compounds and aromatic hydrocarbons,can then still be delivered. In turn, such pure demixing solvent b)stream can then advantageously be recycled and used to extractextraction solvent a), either in step a) itself or in another additionalstep, thereby preventing extraction solvent a) from entering the finalhydrocarbon raffinate stream, without contaminating such raffinatestream with heteroatom containing organic compounds and aromatichydrocarbons. Likewise, such pure extraction solvent a) stream can thenadvantageously be recycled to step a) and used to extract furtherheteroatom containing organic compounds and optional aromatichydrocarbons from fresh feed. Thus, in the present invention,contaminants not removed in step b), will advantageously be concentratedinto the sorption agent(s) as used in such sorption step(s), therebypreventing a build-up of such contaminants in the recycle stream(s) inthe present process.

Because of the above-described use of sorption agent(s) in the presentinvention, there is no need or a substantially reduced need to applyother, cumbersome methods for mitigating a build-up of thesecontaminants. For example, there is no need or a substantially reducedneed to bleed part of the recycle streams before recycling, whereineither (i) such bleed stream is discarded resulting in a loss ofextraction solvent or (ii) the extraction solvent may be recovered fromsuch bleed stream, for example by distillation thereof, which is howevercumbersome.

Further, the present invention relates to a process for the recovery ofaliphatic hydrocarbons from plastics, wherein at least part of theplastics comprises heteroatom containing organic compounds, said processcomprising the steps of:

-   -   (I) cracking the plastics and recovering a hydrocarbon product        comprising aliphatic hydrocarbons, heteroatom containing organic        compounds and optionally aromatic hydrocarbons; and    -   (II) subjecting a liquid hydrocarbon feedstock stream, which        comprises at least part of the hydrocarbon product obtained in        step (I), to the above-mentioned process for the recovery of        aliphatic hydrocarbons from a liquid hydrocarbon feedstock        stream.

Still further, the present invention relates to a process for steamcracking a hydrocarbon feed, wherein the hydrocarbon feed comprisesaliphatic hydrocarbons as recovered in one of the above-mentionedprocesses for the recovery of aliphatic hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of the process for the recovery of aliphatichydrocarbons in accordance with the present invention.

FIG. 2 shows another embodiment of the above-mentioned process.

DETAILED DESCRIPTION OF THE INVENTION

Each of the processes of the present invention comprises multiple steps.In addition, said process may comprise one or more intermediate stepsbetween consecutive steps. Further, said process may comprise one ormore additional steps preceding the first step and/or following the laststep. For example, in a case where said process comprises steps a), b)and c), said process may comprise one or more intermediate steps betweensteps a) and b) and between steps b) and c). Further, said process maycomprise one or more additional steps preceding step a) and/or followingstep c).

Within the present specification, a phrase like “step y) comprisessubjecting at least part of the stream resulting from step x) to” means“step y) comprises subjecting part or all of the stream resulting fromstep x) to” or, similarly, “step y) comprises partially or completelysubjecting the stream resulting from step x) to”. For example, thestream resulting from step x) may be split into one or more partswherein at least one of these parts may be subjected to step y).Further, for example, the stream resulting from step x) may be subjectedto an intermediate step between steps x) and y) resulting in a furtherstream at least part of which may be subjected to step y).

While the process(es) of the present invention and the stream(s) andcomposition(s) used in said process(es) are described in terms of“comprising”, “containing” or “including” one or more various describedsteps and components, respectively, they can also “consist essentiallyof” or “consist of” said one or more various described steps andcomponents, respectively.”.

In the context of the present invention, in a case where a streamcomprises two or more components, these components are to be selected inan overall amount not to exceed 100%.

Further, where upper and lower limits are quoted for a property then arange of values defined by a combination of any of the upper limits withany of the lower limits is also implied.

Within the present specification, by “substantially no” in relation tothe amount of a specific component in a stream, it is meant an amountwhich is at most 1,000, preferably at most 500, more preferably at most100, more preferably at most 50, more preferably at most 30, morepreferably at most 20, and most preferably at most 10 ppmw (parts permillion by weight) of the component in question, based on the amount(i.e. weight) of said stream.

Within the present specification, by “top stream” or “bottom stream”from a column reference is made to a stream which exits the column at aposition, which is between 0% and 30%, more suitably between 0% and 20%,even more suitably between 0% and 10%, based on the total column length,from the top of the column or the bottom of the column, respectively.

Unless indicated otherwise, where in the present specification referenceis made to a boiling point this means the boiling point at 760 mm Hgpressure (101.3 kPa).

Liquid Hydrocarbon Feedstock Stream

In the present invention, the liquid hydrocarbon feedstock streamcomprises aliphatic hydrocarbons, heteroatom containing organiccompounds and optionally aromatic hydrocarbons.

Preferably, the liquid hydrocarbon feedstock stream comprises bothaliphatic hydrocarbons having a boiling point of from 30 to 300° C. andaliphatic hydrocarbons having a boiling point of from greater than 300to 600° C. in a weight ratio of from 99:1 to 1:99. The amount ofaliphatic hydrocarbons having a boiling point of from 30 to 300° C.,based on the total amount of aliphatic hydrocarbons having a boilingpoint of from 30 to 600° C., may be at most 99 wt. % or at most 80 wt. %or at most 60 wt. % or at most 40 wt. % or at most 30 wt. % or at most20 wt. % or at most 10 wt. %. Further, the amount of aliphatichydrocarbons having a boiling point of from 30 to 300° C., based on thetotal amount of aliphatic hydrocarbons having a boiling point of from 30to 600° C., may be at least 1 wt. % or at least 5 wt. % or at least 10wt. % or at least 20 wt. % or at least 30 wt. %.

Thus, advantageously, the liquid hydrocarbon feedstock stream maycomprise varying amounts of aliphatic hydrocarbons within a wide boilingpoint range of from 30 to 600° C. Accordingly, as with the boilingpoint, the carbon number of the aliphatic hydrocarbons in the liquidhydrocarbon feedstock stream may also vary within a wide range, forexample of from 5 to 50 carbon atoms. The carbon number of the aliphatichydrocarbons in the liquid hydrocarbon feedstock stream may be at least4 or at least 5 or at least 6 and may be at most 50 or at most 40 or atmost 30 or at most 20.

The amount of aliphatic hydrocarbons in the liquid hydrocarbon feedstockstream, based on the total weight of the liquid hydrocarbon feedstockstream, may be at least 30 wt. % or at least 50 wt. % or at least 80 wt.% or at least 90 wt. % or at least 95 wt. % or at least 99 wt. % and maybe smaller than 100 wt. % or at most 99 wt. % or at most 90 wt. % or atmost 80 wt. % or at most 70 wt. %. The aliphatic hydrocarbons may becyclic, linear and branched.

The aliphatic hydrocarbons in the liquid hydrocarbon feedstock streammay comprise non-olefinic (paraffinic) and olefinic aliphatic compounds.The amount of paraffinic aliphatic compounds in the liquid hydrocarbonfeedstock stream, based on the total weight of the liquid hydrocarbonfeedstock stream, may be at least 20 wt. % or at least 40 wt. % or atleast 60 wt. % or at least 80 wt. % and may be smaller than 100 wt. % orat most 99 wt. % or at most 80 wt. % or at most 60 wt. %. Further, theamount of olefinic aliphatic compounds in the liquid hydrocarbonfeedstock stream, based on the total weight of the liquid hydrocarbonfeedstock stream, may be smaller than 100 wt. % or at least 20 wt. % orat least 40 wt. % or at least 60 wt. % or at least 80 wt. % and may beat most 99 wt. % or at most 80 wt. % or at most 60 wt. %.

Further, the olefinic compounds may comprise aliphatic compounds havingone carbon-carbon double bond (mono-olefins) and/or aliphatic compoundshaving two or more carbon-carbon double bonds which latter compounds maybe conjugated or non-conjugated. That is to say, the two or morecarbon-carbon double bonds may be conjugated or not conjugated. Thealiphatic compounds having two or more carbon-carbon double bonds mayinclude compounds having double bonds at alpha and omega positions. Theamount of mono-olefins in the liquid hydrocarbon feedstock stream, basedon the total weight of the liquid hydrocarbon feedstock stream, may beat least 20 wt. % or at least 40 wt. % or at least 60 wt. % or at least80 wt. % and may be smaller than 100 wt. % or at most 99 wt. % or atmost 80 wt. % or at most 60 wt. %. Further, the amount of conjugatedaliphatic compounds having two or more carbon-carbon double bonds in theliquid hydrocarbon feedstock stream, based on the total weight of theliquid hydrocarbon feedstock stream, may be greater than 0 wt. % or atleast 10 wt. % or at least 20 wt. % or at least 40 wt. % or at least 60wt. % and may be at most 80 wt. % or at most 60 wt. % or at most 40 wt.%.

Within the present specification, an aliphatic hydrocarbon whichcontains one or more heteroatoms is a “heteroatom containing organiccompound” as further described below. Unless indicated otherwise, eitherexplicitly or by context, within the present specification, the term“aliphatic hydrocarbons” does not include heteroatom containingaliphatic hydrocarbons. Further, unless indicated otherwise, eitherexplicitly or by context, within the present specification, the term“aliphatic hydrocarbons” does not include conjugated aliphatic compoundshaving two or more carbon-carbon double bonds.

In addition to the above-described aliphatic hydrocarbons, the liquidhydrocarbon feedstock stream comprises heteroatom containing organiccompounds and optionally aromatic hydrocarbons.

The amount of aromatic hydrocarbons in the liquid hydrocarbon feedstockstream, based on the total weight of the liquid hydrocarbon feedstockstream, may be 0 wt. % or greater than 0 wt. % or at least 5 wt. % or atleast 10 wt. % or at least 15 wt. % or at least 20 wt. % or at least 25wt. % or at least 30 wt. % and may be at most 50 wt. % or at most 40 wt.% or at most 30 wt. % or at most 20 wt. %. The aromatic hydrocarbons maycomprise monocyclic and/or polycyclic aromatic hydrocarbons. An exampleof a monocyclic aromatic hydrocarbon is styrene. The polycyclic aromatichydrocarbons may comprise non-fused and/or fused polycyclic aromatichydrocarbons. An example of a non-fused polycyclic aromatic hydrocarbonis oligostyrene. Styrene and oligostyrene may originate frompolystyrene. Examples of fused polycyclic aromatic hydrocarbons arenaphthalene and anthracene, as well as alkyl naphthalene and alkylanthracene. The aromatic ring or rings in the aromatic hydrocarbons maybe substituted by one or more hydrocarbyl groups, including alkyl groups(saturated) and alkylene groups (unsaturated).

Within the present specification, an aromatic hydrocarbon which containsone or more heteroatoms is a “heteroatom containing organic compound” asfurther described below. Unless indicated otherwise, either explicitlyor by context, within the present specification, the term “aromatichydrocarbons” does not include heteroatom containing aromatichydrocarbons.

Further, the amount of heteroatom containing organic compounds in theliquid hydrocarbon feedstock stream, based on the total weight of theliquid hydrocarbon feedstock stream, is greater than 0 wt. % and may beat least 0.5 wt. % or at least 1 wt. % or at least 3 wt. % or at least 5wt. % or at least 10 wt. % or at least 15 wt. % or at least 20 wt. % andmay be at most 30 wt. % or at most 20 wt. % or at most 10 wt. % or atmost 5 wt. %.

The heteroatom containing organic compounds in the liquid hydrocarbonfeedstock stream contain one or more heteroatoms, which may be oxygen,nitrogen, sulfur and/or a halogen, such as chlorine, suitably oxygen,nitrogen and/or a halogen. The heteroatom containing organic compoundsmay comprise one or more of the following moieties: amine, imine,nitrile, alcohol, ether, ketone, aldehyde, ester, acid, amide, carbamate(occasionally named urethane) and urea.

Further, the above-mentioned heteroatom containing organic compounds maybe aliphatic or aromatic. An example of an aliphatic, heteroatomcontaining organic compound is oligomeric polyvinyl chloride (PVC).Oligomeric PVC may originate from polyvinyl chloride. Aromatic,heteroatom containing organic compounds may comprise monocyclic and/orpolycyclic aromatic, heteroatom containing organic compounds. Examplesof monocyclic aromatic, heteroatom containing organic compounds areterephthalic acid and benzoic acid. An example of a polycyclic aromatic,heteroatom containing organic compound is oligomeric polyethyleneterephthalate (PET). Terephthalic acid, benzoic acid and oligomeric PETmay originate from polyethylene terephthalate. Examples of nitrogencontaining organic compounds are compounds originating from polyurethaneand polyamides including nylon.

Unless indicated otherwise, either explicitly or by context, within thepresent specification, the term “heteroatom containing organiccompounds” means heteroatom containing organic compounds in ororiginating from the liquid hydrocarbon feedstock stream. Further,unless indicated otherwise, either explicitly or by context, within thepresent specification, the term “heteroatom containing organiccompounds” does not include the extraction solvent, demixing solventand/or washing solvent as defined in the present specification.

Additionally, the liquid hydrocarbon feedstock stream may comprisesalts. Said salts may comprise organic and/or inorganic salts. The saltsmay comprise ammonium, an alkali metal, an alkaline earth metal or atransition metal as the cation and a carboxylate, sulphate, phosphate ora halide as the anion.

Preferably, at least part of the components in the liquid hydrocarbonfeedstock stream, which comprises aliphatic hydrocarbons, heteroatomcontaining organic compounds and optionally aromatic hydrocarbons, aresynthetic compounds, and not natural compounds as present in for examplefossil oil. For example, such synthetic compounds include compoundsoriginating from the pyrolysis of plastics synthesized from biomass, forexample polyethylene synthesized from bio-ethanol through dehydration ofthe ethanol and subsequent polymerization of the ethylene thus formed.

Further, since in the present process heteroatom containing organiccompounds are easily removed, the feed to the present process canadvantageously tolerate a relatively high amount of such heteroatomcontaining organic compounds. Thus, waste plastic that may be pyrolyzedto produce a feed to the present process may compriseheteroatom-containing plastics, such as polyvinyl chloride (PVC),polyethylene terephthalate (PET) and polyurethane (PU). In specific,mixed waste plastic may be pyrolyzed that in addition to heteroatom-freeplastics, such as polyethylene (PE) and polypropylene (PP), contains arelatively high amount of such heteroatom-containing plastics.

Step a)—Extraction with Extraction Solvent a)

In step a) of the present process, at least part of the liquidhydrocarbon feedstock stream, comprising aliphatic hydrocarbons,heteroatom containing organic compounds and optionally aromatichydrocarbons, is contacted with an extraction solvent a) which containsone or more heteroatoms, and the liquid hydrocarbon feedstock stream issubjected to liquid-liquid extraction with the extraction solvent a),resulting in a first stream comprising aliphatic hydrocarbons and asecond stream comprising extraction solvent a), heteroatom containingorganic compounds and optionally aromatic hydrocarbons.

In step a) of the present process, the liquid hydrocarbon feedstockstream may be fed to a first column (first extraction column). Further,a first solvent stream which comprises the extraction solvent a) may befed to the first column at a position which is higher than the positionat which the liquid hydrocarbon feedstock stream is fed, therebyenabling a counterflow liquid-liquid extraction and resulting in a topstream from the first column (above “first stream”) comprising aliphatichydrocarbons and a bottom stream from the first column (above “secondstream”) comprising extraction solvent a), heteroatom containing organiccompounds and optionally aromatic hydrocarbons.

In step a), the weight ratio of the extraction solvent a) to the liquidhydrocarbon feedstock stream may be at least 0.05:1 or at least 0.2:1 orat least 0.5:1 or at least 1:1 or at least 2:1 or at least 3:1 and maybe at most 5:1 or at most 3:1 or at most 2:1 or at most 1:1. Further,the temperature in step a) may be at least 0° C. or at least 20° C. orat least 30° C. or at least 40° C. or at least 50° C. and may be at most200° C. or at most 150° C. or at most 100° C. or at most 70° C. or atmost 60° C. or at most 50° C. or at most 40° C. The pressure in step a)may be at least 100 mbara or at least 500 mbara or at least 1 bara or atleast 1.5 bara or at least 2 bara and may be at most 50 bara or at most30 bara or at most 20 bara or at most 15 bara or at most 10 bara or atmost 5 bara or at most 3 bara or at most 2 bara or at most 1.5 bara. Thetemperature and pressure in step a) are preferably such that both thehydrocarbons from the feedstock stream and the extraction solvent a) arein the liquid state.

In step a), aliphatic hydrocarbons are recovered by liquid-liquidextraction of heteroatom containing organic compounds and optionallyaromatic hydrocarbons with extraction solvent a). Further, preferably,the recovered aliphatic hydrocarbons comprise aliphatic hydrocarbonshaving a boiling point of from 30 to 300° C. and aliphatic hydrocarbonshaving a boiling point of from greater than 300 to 600° C. in a weightratio of from 99:1 to 1:99. The above description of the weight ratio ofaliphatic hydrocarbons having a boiling point of from 30 to 300° C. toaliphatic hydrocarbons having a boiling point of from greater than 300to 600° C. in relation to aliphatic hydrocarbons in the liquidhydrocarbon feedstock stream also applies to the recovered aliphatichydrocarbons.

In step a), said liquid-liquid extraction results in a first streamcomprising aliphatic hydrocarbons and a second stream comprisingextraction solvent a), heteroatom containing organic compounds andoptionally aromatic hydrocarbons. Within the present specification, theformer stream (first stream) comprising recovered aliphatic hydrocarbonsmay also be referred to as a “raffinate stream” and the latter stream(second stream) may also be referred to as an “extract stream”. Suchraffinate stream has a reduced content of aromatic hydrocarbons,conjugated aliphatic compounds having two or more carbon-carbon doublebonds, and heteroatom containing organic compounds. Such raffinatestream comprises no or at most 10 wt. % or at most 5 wt. % or at most 1wt. % or substantially no aromatic hydrocarbons. Further, such raffinatestream comprises no or at most 15 wt. % or at most 10 wt. % or at most 5wt. % or at most 1 wt. % or substantially no conjugated aliphaticcompounds having two or more carbon-carbon double bonds. Further, suchraffinate stream comprises no or at most 1 wt. % or substantially noheteroatom containing organic compounds.

The extraction solvent a) used in step a) of the present process, whichmay be fed as a first solvent stream to a first column in step a),preferably has a density which is at least 3% or at least 5% or at least8% or at least 10% or at least 15% or at least 20% higher than thedensity of the liquid hydrocarbon feedstock stream. Further, saiddensity may be at most 50% or at most 40% or at most 35% or at most 30%higher than the density of the liquid hydrocarbon feedstock stream.

Further, the extraction solvent a) used in step a) contains one or moreheteroatoms, which may be oxygen, nitrogen and/or sulfur. Still further,it is preferred that said extraction solvent a) is thermally stable at atemperature of 200° C. Still further, said extraction solvent a) mayhave a boiling point which is at least 50° C. or at least 80° C. or atleast 100° C. or at least 120° C. and at most 300° C. or at most 200° C.or at most 150° C. Still further, it is preferred that said extractionsolvent a) has no or a relatively low miscibility in heptane.Preferably, extraction solvent a) has such miscibility in heptane thatat most 30 wt. % or at most 20 wt. % or at most 10 wt. % or at most 3wt. % or at most 1 wt. % of extraction solvent a), based on weight ofheptane, is miscible in heptane. The miscibility of a certain compoundin another compound, such as heptane, may be determined by any generalmethod known to a skilled person in the art, including ASTM methodD1476. Where in the present specification reference is made to themiscibility of a compound in another compound, this means miscibility at25° C.

Further, the extraction solvent a) in step a) may have a Hansensolubility parameter distance R_(a,heptane) with respect to heptane asdetermined at 25° C. of at least 3 MPa^(1/2), preferably at least 5MPa^(1/2), more preferably at least 10 MPa^(1/2), more preferably atleast 15 MPa^(1/2). Further, said R_(a,heptane) for extraction solventa) may be lower than 45 MPa^(1/2) or at most 40 MPa^(1/2), preferably atmost 35 MPa^(1/2), more preferably at most 30 MPa^(1/2), more preferablyat most 25 MPa^(1/2). For example, said R_(a,heptane) forN-methylpyrrolidone (NMP) is 15 MPa^(1/2).

Still further, said extraction solvent a) may have a difference inHansen solubility parameter distance R_(a,heptane) with respect toheptane compared to Hansen solubility parameter distance R_(a,toluene)with respect to toluene (i.e. R_(a,heptane)−R_(a,toluene)) as determinedat 25° C. of at least 1.5 MPa^(1/2), preferably at least 2 MPa^(1/2).Further, said difference in R_(a,heptane) compared to R_(a,toluene) forextraction solvent a) may be at most 4.5 MPa^(1/2), preferably at most 4MPa^(1/2).

Hansen solubility parameters (HSP) can be used as a means for predictingthe likeliness of one component compared to another component. Morespecifically, each component is characterized by three Hansenparameters, each generally expressed in MPa^(0.5): δ_(d), denoting theenergy from dispersion forces between molecules; δ_(p), denoting theenergy from dipolar intermolecular forces between molecules; and δ_(h),denoting the energy from hydrogen bonds between molecules. The affinitybetween compounds can be described using a multidimensional vector thatquantifies these solvent atomic and molecular interactions, as a Hansensolubility parameter (HSP) distance R_(a) which is defined in Equation(1):

(R _(a))²=4(δ_(d2)−δ_(d1))²+(δ_(p2)−δ_(p1))²+(δ_(h2)−δ_(h1))²  (1)

-   -   wherein    -   R_(a)=distance in HSP space between compound 1 and compound 2        (MPa^(0.5))    -   δ_(d1), δ_(p1). δ_(h1)=Hansen (or equivalent) parameter for        compound 1 (in MPa^(0.5))    -   δ_(d2), δ_(p2), δ_(h2)=Hansen (or equivalent) parameter for        compound 2 (in MPa^(0.5))

Thus, the smaller the value for R_(a) for a given solvent calculatedwith respect to the compound to be recovered (i.e., the compound to berecovered being compound 1 and the solvent being compound 2, or viceversa), the higher the affinity of this solvent for the compound to berecovered will be.

Hansen solubility parameters for numerous solvents can be found in,among others, CRC Handbook of Solubility Parameters and Other CohesionParameters, Second Edition by Allan F. M. Barton, CRC press 1991; HansenSolubility Parameters: A User's Handbook by Charles M. Hansen, CRC press2007.

In specific, the extraction solvent a) used in step a) of the presentprocess may comprise ammonia or, preferably, one or more organicsolvents selected from the group consisting of diols and triols,including monoethylene glycol (MEG), monopropylene glycol (MPG), anyisomer of butanediol and glycerol; glycol ethers, includingoligoethylene glycols, including diethylene glycol, triethylene glycoland tetraethylene glycol, and monoalkyl ethers thereof, includingdiethylene glycol ethyl ether; amides, including N-alkylpyrrolidone,wherein the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms,including N-methylpyrrolidone (NMP), formamide and di- and monoalkylformamides and acetamides, wherein the alkyl group may contain 1 to 8 or1 to 3 carbon atoms, including dimethyl formamide (DMF), methylformamide and dimethyl acetamide; dialkylsulfoxide, wherein the alkylgroup may contain 1 to 8 or 1 to 3 carbon atoms, includingdimethylsulfoxide (DMSO); sulfones, including sulfolane; N-formylmorpholine (NFM); furan ring containing components and derivativesthereof, including furfural, 2-methyl-furan, furfuryl alcohol andtetrahydrofurfuryl alcohol; hydroxy esters, including lactates,including methyl and ethyl lactate; trialkyl phosphates, includingtriethyl phosphate; phenolic compounds, including phenol and guaiacol;benzyl alcoholic compounds, including benzyl alcohol; aminic compounds,including ethylenediamine, monoethanolamine, diethanolamine andtriethanolamine; nitrile compounds, including acetonitrile andpropionitrile; trioxane compounds, including 1,3,5-trioxane; carbonatecompounds, including propylene carbonate and glycerol carbonate; andcycloalkanone compounds, including dihydrolevoglucosenone.

More preferably, said extraction solvent a) comprises one or more ofabove-mentioned dialkylsulfoxide, in specific DMSO; sulfones, inspecific sulfolane; above-mentioned N-alkylpyrrolidone, in specific NMP;and a furan ring containing component, in specific furfural. Even morepreferably, said extraction solvent a) comprises one or more ofabove-mentioned N-alkylpyrrolidone, in specific NMP, and a furan ringcontaining component, in specific furfural. Most preferably, extractionsolvent a) comprises NMP.

An aqueous solution of a quaternary ammonium salt, in specific trioctylmethyl ammonium chloride or methyl tributyl ammonium chloride, may alsobe used as the extraction solvent a) in step a).

In addition to extraction solvent a), a washing solvent, such as water,may also be added to step a). This washing solvent is herein referred toas washing solvent c) and is further described below. In such case, stepa) preferably results in a first stream comprising aliphatichydrocarbons and a second stream comprising washing solvent c),extraction solvent a), heteroatom containing organic compounds andoptionally aromatic hydrocarbons. Thus, advantageously, said washingsolvent c) as added in step a), functions as an extraction solventextracting extraction solvent a) and thereby making it possible that noor substantially no extraction solvent a) ends up in the first streamresulting from step a) and comprising recovered aliphatic hydrocarbons.In case washing solvent c) is also added to step a), the weight ratio ofextraction solvent a) to washing solvent c) in step a) may be at least0.5:1 or at least 1:1 or at least 2:1 or at least 3:1 and may be at most30:1 or at most 25:1 or at most 20:1 or at most 15:1 or at most 10:1 orat most 5:1 or at most 3:1 or at most 2:1.

In case washing solvent c) is also added to step a), a second solventstream which comprises washing solvent c) may be fed to theabove-mentioned first column (first extraction column) at a positionwhich is higher than the position at which the above-mentioned firstsolvent stream which comprises the extraction solvent a) is fed, therebyenabling a counterflow liquid-liquid extraction and resulting in a topstream from the first column (above “first stream”) comprising aliphatichydrocarbons and a bottom stream from the first column (above “secondstream”) comprising washing solvent c), extraction solvent a),heteroatom containing organic compounds and optionally aromatichydrocarbons. In the above case, the first solvent stream in extractionstep a) may comprise demixing solvent b), such as water, and/orabove-mentioned optional washing solvent c) in addition to extractionsolvent a). Demixing solvent b) is also further described below. Saiddemixing solvent b) and washing solvent c) may originate from one ormore recycle streams after step c) of the present process.

In case washing solvent c) is also added to step a), it is preferredthat the stream comprising washing solvent c) to be added comprises noor substantially no heteroatom containing organic compounds originatingfrom the liquid hydrocarbon feedstock stream. This preference appliesespecially in a case where said stream is fed to the first extractioncolumn at a relatively high position, as described above, where theseheteroatom containing organic compounds could re-contaminate theraffinate (top) stream resulting from step a). Advantageously, in thepresent invention, at least part of the demixing solvent b) containingstream resulting from step c) or at least part of the demixing solventb) containing treated stream resulting from sorption step (ii), whichmay contain no or substantially no heteroatom containing organiccompounds, may be used as such washing solvent c) stream for feeding(recycling) to step a), especially in case demixing solvent b) isidentical to washing solvent c), especially water.

As mentioned above, the second stream resulting from step a), whichstream for the above-mentioned first (extraction) column correspondswith the bottom stream from such column, comprises extraction solventa), heteroatom containing organic compounds and optionally aromatichydrocarbons. Said stream may additionally comprise salts and/orconjugated aliphatic compounds having two or more carbon-carbon doublebonds in a case wherein such salts and/or compounds are present in theliquid hydrocarbon feedstock stream.

In the present invention, extraction solvent a) is recovered from thesecond stream resulting from step a) and then advantageously recycled tostep a), through steps b), c) and d) of the present process.

Step b)—Demixing with Demixing Solvent b)

In step b) of the present process, at least part of the second streamresulting from step a), comprising extraction solvent a), heteroatomcontaining organic compounds and optionally aromatic hydrocarbons, ismixed with a demixing solvent b) which contains one or more heteroatomsand has a miscibility in heptane which is lower than the miscibility ofextraction solvent a) in heptane, and the resulting mixture is separatedinto a first stream comprising heteroatom containing organic compoundsand optionally aromatic hydrocarbons and a second stream comprisingextraction solvent a), demixing solvent b), heteroatom containingorganic compounds and optionally aromatic hydrocarbons. Depending on thepartition coefficient, a certain amount of heteroatom containing organiccompounds and any aromatic hydrocarbons also ends up in said secondstream, wherein the first stream is more hydrophobic than the secondstream. Thus, said second stream additionally comprises heteroatomcontaining organic compounds and optionally aromatic hydrocarbons.

The demixing solvent b) used in step b) contains one or moreheteroatoms, which may be oxygen, nitrogen and/or sulfur. Still further,it is preferred that just like extraction solvent a), said demixingsolvent b) has no or a relatively low miscibility in heptane.Preferably, demixing solvent b) has such miscibility in heptane that atmost 10 wt. % or at most 3 wt. % or at most 1 wt. % or at most 0.5 wt. %or at most 0.1 wt. % of demixing solvent b), based on weight of heptane,is miscible in heptane. In the present invention, the miscibility ofdemixing solvent b) in heptane is lower than the miscibility ofextraction solvent a) in heptane. The miscibility of said solvents a)and b) in heptane may be determined by any general method known to askilled person in the art, including above-mentioned ASTM method D1476.

Further, suitably, demixing solvent b) is miscible in extraction solventa). This implies that up to 50 wt. % of demixing solvent b), based ontotal amount of demixing solvent b) and extraction solvent a), can bemixed in extraction solvent a).

Further, the demixing solvent b) in step b) may have a Hansen solubilityparameter distance R_(a,heptane) with respect to heptane as determinedat 25° C. of at least 10 MPa^(1/2), preferably at least 20 MPa^(1/2),more preferably at least 30 MPa^(1/2), more preferably at least 40MPa^(1/2). Further, said R_(a,heptane) for demixing solvent b) may be atmost 55 MPa^(1/2), more preferably at most 50 MPa^(1/2), more preferablyat most 45 MPa^(1/2). For example, said R_(a,heptane) for water is 45MPa^(1/2).

As mentioned above, the miscibilities, in heptane, of extraction solventa) and demixing solvent b) are different. Hence, said solvents a) and b)are not identical. In specific, demixing solvent b) may have a Hansensolubility parameter distance R_(a,heptane) with respect to heptane asdetermined at 25° C. which is greater than such R_(a,heptane) forextraction solvent a). Preferably, said difference in R_(a,heptane) forsolvents a) and b) is at least 1 MPa^(1/2), more preferably at least 5MPa^(1/2), more preferably at least 10 MPa^(1/2), more preferably atleast 15 MPa^(1/2), more preferably at least 20 MPa^(1/2), morepreferably at least 25 MPa^(1/2). Further, preferably, said differencein R_(a,heptane) for solvents a) and b) is at most 55 MPa^(1/2), morepreferably at most 50 MPa^(1/2), more preferably at most 45 MPa^(1/2),more preferably at most 40 MPa^(1/2), more preferably at most 35MPa^(1/2), more preferably at most 30 MPa^(1/2).

In specific, the demixing solvent b) used in step b) of the presentprocess may comprise one or more solvents selected from the groupconsisting of water and the solvents from the group of solvents asdefined hereinabove for extraction solvent a). Preferably, said demixingsolvent b) comprises one or more of water and above-mentioned diols andtriols, in specific monoethylene glycol (MEG) and glycerol. Morepreferably, demixing solvent b) comprises water, most preferablyconsists of water. Other preferences and embodiments as described abovewith reference to the extraction solvent a) used in step a) also applyto demixing solvent b), with the exception that demixing solvent b) isnot identical to extraction solvent a), as it has a lower miscibility inheptane, and that demixing solvent b) may comprise and preferablycomprises water.

Further, the second stream resulting from step b) may additionallycomprise salts. Any conjugated aliphatic compounds having two or morecarbon-carbon double bonds may end up in the first or second streamresulting from step b), together with heteroatom containing organiccompounds and optionally aromatic hydrocarbons. Generally, in thepresent invention, said conjugated aliphatic compounds may behavesimilarly as aromatic compounds so that these may end up in the samestream or streams as the optional aromatic hydrocarbons.

In step b), demixing solvent b) is added, separately from the secondstream resulting from step a), and in addition to any demixing solventb) that may be present in the latter stream, and mixed with the latterstream. In step b), at least part of a second stream comprising washingsolvent c), such as water, and extraction solvent a), resulting from thebelow-described optional, additional extraction step wherein at leastpart of the first stream resulting from step a), wherein said firststream comprises recovered aliphatic hydrocarbons and extraction solventa), is subjected to liquid-liquid extraction with a washing solvent c),may be added to provide for said demixing solvent b) that needs to beadded in step b).

The mixing in step b) may be performed in any way known to a skilledperson. For example, a mixer may be used upstream of a phase separationapparatus as described below. Further, for example, in-line (or static)mixing may be performed upstream of such phase separation apparatus.Still further, mixing may be effected in a column as described below.

Through such addition of demixing solvent b) and mixing in step b),different phases are formed including a more hydrophobic, first phaseand a less hydrophobic, second phase comprising extraction solvent a),demixing solvent b), heteroatom containing organic compounds andoptionally aromatic hydrocarbons, which phases are separated in step b)into said first stream and second stream, respectively. Thus,advantageously, said demixing solvent b) as added in step b) separatelyfrom the second stream resulting from step a), functions as a so-called“demixer” (or “antisolvent”), thereby removing the more hydrophobiccompounds from the extraction solvent a) to be recovered and recycled.

The phase separation in step b) may be performed by any apparatuscapable of separating two phases, including a decanter, a flotationdevice, a coalescer and a centrifuge, suitably a decanter. It ispreferred that the phase separation in step b) is carried out in asingle stage, for example in a decanter, a flotation device, a coalesceror a centrifuge. For example, when using a decanter in step b), a first,upper phase comprising more hydrophobic compounds and a second, lowerphase comprising extraction solvent a), demixing solvent b) and lesshydrophobic compounds (i.e. less hydrophobic than compounds in saidfirst phase) may be separated into said first stream and second stream,respectively.

Further, step b) may be carried out in a column comprising multipleseparation stages. In the latter case, step b) comprises mixing at leastpart of the second stream resulting from step a), respectively, withdemixing solvent b) in the column and separating the resulting mixtureinto the above-mentioned first stream and second stream, suitablyresulting in a top stream from the column (above “first stream”) and abottom stream from the column (above “second stream”). Preferably, saiddemixing solvent b) and the other, extraction solvent a) rich stream arefed co-currently to the column, at the bottom thereof.

Internals in the above-mentioned column contribute to the mixing of theextraction solvent a) rich stream and the demixing solvent b). Suchcolumn internals are known in the art. The column internals may comprisea packing such as Raschig rings, Pall rings, Lessing rings, Bialeckirings, Dixon rings; sieving plates; or a random structured packing,among others, as described in Perry's Chemical Engineer's Handbook.Furthermore, the column may be provided with stirring means. Forexample, a shaft may run along the column and may be provided withrotors and stators fixed to the column.

Further, the above description of temperature and pressure in extractionstep a) also applies to step b). Still further, in step b), the weightratio of the demixing solvent b) to the extraction solvent a), based onthe amount of extraction solvent a) in the second stream resulting fromstep a), may be at least 0.005:1 or at least 0.01:1 or at least 0.5:1 orat least 1:1 or at least 2:1 and may be at most 10:1 or at most 7:1 orat most 5:1 or at most 4:1 or at most 2:1. Suitably, the amount ofdemixing solvent b) added in step b), based on total amount of (i) saidamount of demixing solvent b) and (ii) the amount of extraction solventa) in the second stream resulting from step a), may be of from 0.1 to 45wt. %, more suitably of from 1 to 40 wt. %, more suitably of from 5 to35 wt. %, more suitably of from 10 to 30 wt. %.

Thus, advantageously, in step b) part of the heteroatom containingorganic compounds and optional aromatic hydrocarbons are removed fromthe extraction solvent a) to be recycled, so that there is no need toseparate the extraction solvent a) from such removed compounds in alater step, for example by means of distillation which is cumbersome andenergy consuming. Further, advantageously, any aromatic hydrocarbons andconjugated aliphatic compounds having two or more carbon-carbon doublebonds removed in step b) may be blended with pygas and processed intofuel or used in the production of aromatic compounds. Likewise, theheteroatom containing organic compounds removed in step b) may also beconverted into fuel, optionally after a hydrotreatment to remove theheteroatoms. Further, said compounds removed in step b) may be furtherseparated into various fractions which may be used as solvents.

Step c)—Separation of Extraction Solvent a) and Demixing Solvent b)

In step c) of the present process, at least part of the second streamresulting from step b), and comprising extraction solvent a) anddemixing solvent b), is separated into a first stream comprisingdemixing solvent b) and a second stream comprising extraction solventa). In case the below-described optional washing solvent c) is used inthe present invention, which washing solvent c) may be identical to ordifferent from, preferably identical to, demixing solvent b), suchwashing solvent c) may end up in said second stream resulting from stepb) and subsequently in said first stream resulting from step c).

Thus, a feed stream to step c) comprises at least part of the secondstream resulting from step b). In step c), demixing solvent b) andextraction solvent a) may be separated from each other in any known way,preferably by evaporation, for example through distillation. The latterseparation may be performed in a distillation column. Advantageously, indistillation, at least part of any heteroatom containing organiccompounds and aromatic hydrocarbons in the feed stream to step c) isremoved azeotropically with the demixing solvent b), especially water.

Thus, it is preferred that step c) comprises separating at least part ofthe second stream resulting from step b), by distillation into a topstream comprising demixing solvent b) and a bottom stream comprisingextraction solvent a). In a case wherein the feed stream to step c)additionally comprises heteroatom containing organic compounds andoptionally aromatic hydrocarbons, said top stream additionally comprisessuch compounds.

Further, in a case wherein the feed stream to step c) additionallycomprises salts, the second stream resulting from step c) additionallycomprises such salts. If the feed stream to step c) or the second streamresulting from step c) contains any solid salts, they may be removedtherefrom by any method, including filtering.

In the present invention, the amount of demixing solvent b) in the feedstream to step c) may be at least 10 wt. % or at least 20 wt. % and maybe at most 70 wt. % or at most 50 wt. % or at most 40 wt. %. The secondstream resulting from step c) may still comprise demixing solvent b),for example in an amount of at most 10 wt. % or at most 5 wt. % or atmost 3 wt. % or at most 1 wt. %. Advantageously, in case the amount ofdemixing solvent b) in said second stream is relatively low, for exampleup to 5 wt. %, such demixing solvent b) does not need to be removedbefore extraction solvent a) from said same stream is recycled to stepa) of the present process.

As mentioned above, in a case wherein the feed stream to theabove-mentioned distillation step, as step c) in the present process,comprises heteroatom containing organic compounds and optionallyaromatic hydrocarbons in addition to extraction solvent a) and demixingsolvent b), the top stream resulting from the distillation stepcomprises demixing solvent b), heteroatom containing organic compoundsand optionally aromatic hydrocarbons. For, advantageously, indistillation, at least part of said heteroatom containing organiccompounds and aromatic hydrocarbons is removed azeotropically with thedemixing solvent b), especially water. In the latter case, said topstream may be separated into two phases, one phase comprising demixingsolvent b) and another phase comprising heteroatom containing organiccompounds and optionally aromatic hydrocarbons. Such phase separationmay be performed by any apparatus capable of separating two phases,including a decanter, a flotation device, a coalescer and a centrifuge,suitably a decanter. Advantageously, demixing solvent b) from suchseparated phase comprising demixing solvent b) may be recycled asfurther described below, whereas the other phase may be bled from theprocess thereby reducing the risk of any build-up of heteroatomcontaining organic compounds and aromatic hydrocarbons in the presentprocess.

Sorption Steps (i) and (ii)

In the present invention, advantageously, a sorption agent is used insteps (i) and (ii) to remove heteroatom containing organic compounds andoptionally aromatic hydrocarbons, which are not completely removed instep b) but which are entrained in the second stream resulting from stepb) which comprises extraction solvent a) and demixing solvent b) to beseparated from each other in subsequent step c). By such sorption,advantageously, a build-up of these contaminants in the recyclestream(s) in the present process is avoided.

It is envisaged that the removal of heteroatom containing organiccompounds and optionally aromatic hydrocarbons by the above-mentionedsorption is applied in the present process in either or both of thefollowing steps:

-   -   (i) before step c): contacting at least part of the second        stream resulting from step b), which stream comprises extraction        solvent a), demixing solvent b), heteroatom containing organic        compounds and optionally aromatic hydrocarbons, with a sorption        agent; and/or    -   (ii) after step c): contacting at least part of the first stream        resulting from step c), wherein that stream comprises demixing        solvent b), heteroatom containing organic compounds and        optionally aromatic hydrocarbons, with a sorption agent.

Further, sorption step (ii) is performed before any recycle of at leastpart of the demixing solvent b) from the first stream resulting fromstep c), as for example in optional recycle step e). Further, step (ii)is preferably performed before any recycle of at least part of the firststream resulting from step c) to step c).

In this way, at least part of the contaminants will advantageously beconcentrated into the sorption agent(s) as used in such sorptionstep(s), thereby preventing a build-up of such contaminants in therecycle stream(s) in the present process. Thus, the sorption agentretains contaminants, which sorption agent may eventually be regeneratedor be removed from the process and replaced by fresh sorption agent,thereby avoiding the risk of a build-up of heteroatom containing organiccompounds and aromatic hydrocarbons in the present process.

The treated streams resulting from sorption steps (i) and (ii)preferably comprise no or substantially no heteroatom containing organiccompounds and aromatic hydrocarbons.

In case of sorption step (i), at least part of the treated streamresulting from sorption step (i) and comprising demixing solvent b) andextraction solvent a) may be fed to step c) wherein it is separated intoa first stream comprising demixing solvent b) and a second streamcomprising extraction solvent a). At least part of the extractionsolvent a) from the second stream resulting from step c) is recycled asfurther described below. Advantageously, there is no need to separateheteroatom containing organic compounds and aromatic hydrocarbons fromsaid first stream, as the major part of these contaminants has alreadybeen removed in sorption step (i). Consequently, at least part of thedemixing solvent b) from said first stream may be recycled as furtherdescribed below.

Further, in case of sorption step (ii), at least part of the demixingsolvent b) from the treated stream resulting from sorption step (ii) maybe recycled as further described below. As mentioned above, in step c),extraction solvent a) and demixing solvent b) may be separated from eachother by distillation, wherein at least part of any heteroatomcontaining organic compounds and aromatic hydrocarbons in the feedstream to step c) is removed azeotropically with the demixing solventb). Generally, the relative amount of demixing solvent b) in the topstream resulting from such distillation is relatively high as comparedto the amount of the contaminants, comprising said heteroatom containingorganic compounds and optional aromatic hydrocarbons, so that it may becumbersome to remove these contaminants by phase separation whereby suchcontaminants less readily form a separate phase upon condensation. Suchcumbersome phase formation and separation may advantageously beprevented in the present invention through performing above-describedsorption steps (i) and/or (ii).

In the present specification, sorption means a process in which onesubstance (the sorption agent) takes up or holds another substance byabsorption, adsorption or a combination of both. Preferably, thesorption agent used in the present invention is a sorption agent, whichpreferentially sorbs heteroatom containing organic compounds andoptionally aromatic hydrocarbons. In specific, it is preferred thatheteroatom containing organic compounds and optionally aromatichydrocarbons are preferentially sorbed as compared to the extractionsolvent, demixing solvent and/or washing solvent as defined in thepresent specification. In this way, the quality of an extraction solventa) recycle stream, any demixing solvent b) recycle stream and/or anywashing solvent c) recycle stream may advantageously be increased in thepresent process.

Suitably, the sorption agent separates heteroatom containing organiccompounds and optional aromatic hydrocarbons by affinity. Further, thesorption agent may have a relatively low polarity.

In the present invention, the heteroatom containing organic compoundsand optional aromatic hydrocarbons to be removed may be relatively largemolecules as compared to the extraction solvent a), demixing solvent b)and optional washing solvent c). In the present invention, a suitablesorption agent has preferably pore diameters that are large enough topartially or fully sorb heteroatom containing organic compounds andoptional aromatic hydrocarbons.

Sorption agents for use in steps (i) and (ii) of the present processsuitably have a porous structure comprised of micro-, meso- ormacropores or a combination thereof.

According to IUPAC notation, microporous structures have pore diametersof less than 2 nm (20 Å, angstroms), mesoporous structures have porediameters between 2 and 50 nm (20-500 Å), and macroporous structureshave pore diameters greater than 50 nm (500 Å).

Sorption agents which may suitably be used in steps (i) and (ii) are notlimited to the specific materials listed in the present specification.In general, any material characterized by having a relatively highspecific surface area, a porous structure comprising micro-, meso- ormacropores or a combination thereof, from natural origin or synthetic,from a mineral or an organic source, with a treated or untreatedsurface, and in any form may be used in this invention. Said specificsurface area may be in the range of from 1 to 3000 m²/g, preferably 50to 2000 m²/g, more preferably 100 to 1000 m²/g. Said specific surfacearea may be at least 1 m²/g or at least 10 m²/g or at least 50 m²/g.Further, it may be at most 3000 m²/g or at most 1000 m²/g or at most 500m²/g. Furthermore, suitable sorption agents for use in steps (i) and(ii) have a pore volume of at least 0.001 cm³/g or at least 0.01 cm³/gor at least 0.1 cm³/g, and at most 1 cm³/g or at most 3 cm³/g or at most5 cm³/g or at most 10 cm³/g. Suitable sorption agents for use in steps(i) and (ii) may fulfill two from the above-mentioned characteristics,namely pore size and surface area, or pore size and pore volume, orsurface area and pore volume. As mentioned above, a relatively highaffinity of the sorption agent for heteroatom containing organiccompounds and optional aromatic hydrocarbons is preferred.

Sorption agents that may be conveniently used in steps (i) and (ii) ofthe process of the present invention may be molecular sieves ofinorganic origin, such as metal oxides wherein the metal is one or moreof alkaline earth, transition and post-transition metals, such as Al,Si, Zn, Mg, Ti, Zr; or may be molecular sieves of organic origin, suchas activated carbon, cross-linked and porous polymers, carbonaceousmaterials; or may be hybrid molecular sieves, such as metal-organicframeworks. The sorption agent may be dispersed in a porous amorphousinorganic or organic matrix (also referred to as binder material),having channels and cavities therein that enable liquid access to thesorption agent. Alternatively, the sorption agent may be used without abinder material.

Suitable sorption agents for this invention with predominant microporousstructure are zeolites, porous glass, activated carbon, carbon char(“char” stands for “charcoal”), clays such as bauxite, preferablyactivated clays, activated alumina, aerogels, graphene-basednanomaterials and single-wall or multi-wall carbon nanotubes. Suitablesorption agents for this invention with predominant mesoporous structureare ordered mesoporous carbon (OMC), mesoporous activated carbon,mesoporous zeolites, activated alumina, silica gel and mesoporoussilicas such as M-41-S, MAS-5, MCM-41, SBA-15, SBA-16, TUD-1, HMM-33,FSM-16, MSM-48. A suitable sorption agent for this invention withpredominant macroporous structure is macroporous silica.

Sorption agents comprising carbon such as activated carbon and carbonchar, as mentioned above, may consist mainly of carbon, for example, asubstance comprising 80 to 100 wt. % of carbon, preferably 90 to 100 wt.% of carbon, more preferably 95 to 100 wt. %, most preferably 98 to 100wt. % of carbon, and highly preferably 99 to 100 wt. % of carbon.

A preferred activated carbon as sorption agent for removing heteroatomcontaining organic compounds and optionally aromatic hydrocarbons insteps (i) and (ii), especially in step (ii), has an iodine number in therange of from 500 to 1200 mg/g, and a molasses number in the range offrom 95 to 1500, more preferably in the range of from 200 to 1500.“Iodine number” is a relative measure of pores at sizes of 10 to 28Angstroms. It is reported in milligrams of elemental iodine sorbed pergram of granulated activated carbon and determines the area available onthe activated carbon to sorb low molecular weight organic compounds.Iodine number may be determined according to ASTM D4607. “Molassesnumber” measures the degree to which an activated carbon removes colorfrom a stock solution. It measures the pores greater than 28 Angstroms.These are the pores responsible for removing larger molecular weightorganic compounds. In this case, the amount of sorbed molasses isquantified.

Furthermore, suitable activated carbons for this invention have a totalspecific surface area in the range of from 600 to 2000 m²/g and a totalpore volume in the range of from 0.9 to 2.5 ml/g. Still further, apreferred activated carbon for this invention has a specific surfacearea above 100 m²/g and a pore volume above 0.5 ml/g, for pores largerthan 20 Angstroms. These properties are advantageous in removingrelatively large molecules comprising said heteroatom containing organiccompounds and optional aromatic hydrocarbons to be removed in steps (i)and (ii).

Activated carbons and carbon chars, of which the surfaces are modifiedand/or functionalized, may also suitably be used in steps (i) and (ii).Suitable methods to produce functional properties on carbon materialsurfaces include oxidation by liquid and gaseous oxidants, grafting offunctional groups onto the material surfaces, physisorption of ligands,vapor deposition, and/or functional groups developed during carbonactivation processes.

Zeolites are also suitable sorption agents for removing heteroatomcontaining organic compounds and optionally aromatic hydrocarbons insteps (i) and (ii). Zeolites can be produced in several aluminosilicatering arrangements, and zeolites of any framework type may suitably beused in the present invention. Exemplary zeolites for use in steps (i)and (ii) are faujasite-type such as 13X (sodium form of Zeolite X) or10X and NaX, LTA-type such as pore-closed zeolite 4A and zeolite 4A,ZSM-type, and mixtures thereof. Preferably, zeolites for the removal ofheteroatom containing organic compounds in this invention have poresand/or surface cavities with a cross-sectional dimension greater than5.6 Angstroms. Examples of such zeolites include MFI-types such as ZSM-5and Pentasil Zeolite, Mordenite (MOR) types, zeolite L (LTL-type),FAU-types zeolites such as X and Y, dealuminiated zeolite Y, low sodiumUltrastable Y (USY), MTW-type such as ZSM-12, zeolite beta (BEA-type),and zeolite omega (MAZ-type). Furthermore, sorption agents with surfacecavities with a cross-sectional size greater than 5.6 Angstroms,regardless of the dimensions of the pores, are also suitable for sorbingheteroatom containing organic compounds. Examples of such sorptionagents with such surface cavities are MWW-type zeolites such as MCM-22,PSH-3, SSZ-25, MCM-41, MCM-49 and MCM-56, IFR-type zeolites such asMCM-58, MEL-type zeolites such as ZSM-11, FER-type zeolites such asZSM-35, and clinoptilolite, ferrierite, stilbite, EU-1, NU-87,mordenite, faujasites, gmelinite, and cancrinite.

Preferred molecular sieve zeolite-based sorption agents suitable for usein steps (i) and (ii) of this invention, have a relatively low polarityand low affinity for polar components, which may include the heteroatomcontaining organic compounds. The polarity of a molecular sieve zeoliteis determined by its Si/Al ratio, a low ratio resulting in a highpolarity and vice versa. A preferred sorption agent for this inventioncomprises a zeolite with a Si/Al ratio above 20. Such zeolites arerelatively organophilic and may advantageously sorb compounds such asphenol. A suitable example of such preferred sorption agent is MCM-22which has a Si/Al ratio of 30. Alternatively, a preferred sorption agentfor this invention comprises a zeolite with a Si/Al ratio below 20 whichhas undergone a treatment, such as cation exchange or surfacemodification, to increase its affinity for the heteroatom containingorganic compounds and/or aromatic compounds.

Further, molecular sieve zeolites suitable for use as sorption agent insteps (i) and (ii) may be modified by cation exchange. For instance,cationic sites can be filled with one or more metal cations selectedfrom the metals of Groups I-A, I-B, II-B and II-A (IUPAC 1, 11, 12 and2) of the Periodic Table of Elements by ion-exchange. Preferred metalcations for ion exchange include beryllium, lithium, sodium, magnesium,potassium, calcium, rubidium, strontium, cesium, barium, gold, copper,silver, zinc and cadmium.

Furthermore, sorption agents suitable for use in steps (i) and (ii) maybe of the silicalite type, organosilicates or crystalline silicapolymorph. Silicalite type sorption agents have a very high silica toalumina ratio (>1000). Silicalite type sorption agents are not zeolitesbecause they lack ion exchange capacity. Organosilicates are synthesizedfrom reaction systems essentially free of aluminum-containing reagentsand which are either entirely free of framework AlO⁴⁻ tetrahedra orcontain no crystallographically significant amounts thereof.Organosilicates may be made with a combination of alkali metal cations,preferably sodium, potassium or lithium, silica and tetraethylammonium(TEA) cations. Due to their organophilic character, silicalitesadvantageously selectively sorb organic molecules, including heteroatomcontaining organic compounds and any aromatic hydrocarbons, from polarmedia such as water or a mixture of polar media and organic solvent.

Crystalline hybrid porous materials may also be used as sorption agentsin steps (i) and (ii). These may be characterized by a high porosity, ahigh surface area and a low density. There are two classes of hybridporous materials: covalent organic frameworks (COF's) which consistpurely of organic materials, and metal-organic frameworks (MOF's) whichconsist of individual metal cations or clusters of cations mutuallylinked by polyfunctional organic molecules. Both types may suitably beused in the present invention.

Preferably, the sorption agent used in step (i) in the present inventionpreferentially sorbs heteroatom containing organic compounds andoptionally aromatic hydrocarbons and sorbs no or substantially nodemixing solvent b) and extraction solvent a), thereby eventuallyincreasing the quality of the demixing solvent b) recycle and extractionsolvent a) recycle streams. A preferred sorption agent in step (i)comprises a zeolite such as ZSM-12, a silicalite and/or MCM-22.

Preferably, the sorption agent used in step (ii) in the presentinvention preferentially sorbs heteroatom containing organic compoundsand aromatic hydrocarbons and sorbs no or substantially no demixingsolvent b), thereby eventually increasing the quality of the demixingsolvent b) recycle stream(s). A preferred sorption agent material instep (ii) comprises activated carbon.

Temperatures in steps (i) and (ii) may be in the range of from ambienttemperature to about 160° C., preferably of from 40 to 90° C., morepreferably of from 40 to 60° C. In steps (i) and (ii) of this invention,pressure is not critical for the performance of the sorption agent andit can vary in the range of from atmospheric to 100 barg.

Heteroatom containing organic compounds and optionally aromatichydrocarbons build up in sorbent material producing a “spent sorbent”.As it is known in the art, eventually, it is required to replace orregenerate the sorbent. In either case, the corresponding vesselcontaining the spent sorbent is taken out of service. In case ofregeneration, the spent sorbent is put in contact with a stream thatdoes not contain heteroatom containing organic compounds and optionallyaromatic hydrocarbons. Preferably, this stream is heated to facilitatethe desorption of the heteroatom containing organic compounds andoptionally aromatic hydrocarbons. The regeneration stream can be a gas,liquid or supercritical fluid. It can be inert such as nitrogen, orreactive such as hydrogen, oxygen and hydrogen peroxide. Depending onthe regeneration method, regeneration temperatures are in the range offrom 20 to 350° C. Regeneration of the sorbent material can be carriedout by stripping with a stream such as steam, or nitrogen, or by heatingthe sorbent in air to burn off the sorbed material. Alternatively, incase the sorbent material used in the invention cannot be fullyregenerated, it must be discarded when its sorption capacity is reached.

Recycle Steps

In step d) of the present process, at least part of the extractionsolvent a) from the second stream resulting from step c) is recycled tostep a).

The second stream resulting from step c) may additionally comprisearomatic hydrocarbons and/or heteroatom containing organic compounds. Ina case where a stream comprising extraction solvent a) to be recycled tostep a) comprises a relatively high amount of such compounds, additionaldemixing solvent b) may be added to step b) so as to prevent anybuild-up of these contaminants in such recycle stream to step a).Further, these contaminants may be removed before recycling extractionsolvent a) to step a), by bleeding part of the stream comprisingextraction solvent a) to be recycled to step a) wherein either suchbleed stream may be discarded or extraction solvent a) may be recoveredfrom such bleed stream, for example by distillation thereof.

Further, in optional step e) of the present process, at least part ofthe demixing solvent b) from the first stream resulting from step c) isrecycled to step b). In case sorption step (ii) is performed in thepresent process, at least part of the demixing solvent b) from thetreated stream resulting from sorption step (ii) may be recycled in stepe) to step b).

The latter recycle to step b), in step e), is suitable in a case whereinsaid first stream resulting from step c) or said treated streamresulting from sorption step (ii) still comprises a relatively highamount of heteroatom containing organic compounds and/or aromatichydrocarbons originating from the liquid hydrocarbon feedstock stream.However, in a case wherein such stream comprises no or substantially noor a relatively low amount of heteroatom containing organic compoundsand/or aromatic hydrocarbons, which is advantageously enabled by thesorption step(s) in the present process, it is preferred to recycle atleast part of the demixing solvent b) from such stream to step a) incase a washing solvent c), such as water, is added to step a) asdescribed above or to the below-described optional, additionalextraction step wherein such washing solvent c) is added.

Separation of Extraction Solvent a) from Raffinate Stream

In a case wherein the stream comprising recovered aliphatic hydrocarbonsresulting from the liquid-liquid extraction by the extraction solvent a)in step a) (raffinate stream) additionally comprises extraction solventa), it is preferred that extraction solvent a) is separated from thatstream which is the first stream resulting from step a), and isoptionally recycled to step a). In this way, the recovered aliphatichydrocarbons are advantageously separated from any extraction solvent a)in the above-mentioned raffinate stream, and the separated extractionsolvent a) may advantageously be recycled to step a).

Extraction solvent a) may be separated from the above-mentioned firststream resulting from step a), wherein said stream comprises aliphatichydrocarbons and extraction solvent a), in any way, includingdistillation, extraction, absorption and membrane separation.

In specific, in the above-mentioned case wherein the first streamresulting from step a) comprises aliphatic hydrocarbons and extractionsolvent a), in an additional step, at least part of said first stream iscontacted with a washing solvent c) and is subjected to liquid-liquidextraction with the washing solvent c), resulting in a first streamcomprising aliphatic hydrocarbons and a second stream comprising washingsolvent c) and extraction solvent a).

In the present invention, the optional washing solvent c) that may beused in the above-mentioned additional extraction step or that may beseparately added to step a) or that may be added together withextraction solvent a) in a stream to step a), may be identical to ordifferent from, preferably identical to, demixing solvent b). Thepreferences and embodiments as described above with reference todemixing solvent b) also apply to optional washing solvent c).Preferably, washing solvent c) comprises water, more preferably consistsof water. Further, preferably, both demixing solvent b) and washingsolvent c) comprise water, more preferably consist of water.

In the above-mentioned additional step, the first stream resulting fromstep a) and comprising aliphatic hydrocarbons and extraction solvent a)may be fed to a second column (second extraction column). Further, asecond solvent stream which comprises washing solvent c) may be fed tothe second column at a position which is higher than the position atwhich said first stream resulting from step a) is fed, thereby enablinga counterflow liquid-liquid extraction and resulting in a top streamfrom the second column (above “first stream”) comprising aliphatichydrocarbons and a bottom stream from the second column (above “secondstream”) comprising washing solvent c) and extraction solvent a).

Thus, advantageously, said washing solvent c) as added in theabove-mentioned additional step, functions as an extraction solventextracting extraction solvent a) thereby making it possible thatadvantageously no or substantially no extraction solvent a) ends up inthe recovered aliphatic hydrocarbons. In the above-mentioned additionalstep, the weight ratio of extraction solvent a) to washing solvent c)may be at least 0.5:1 or at least 1:1 or at least 2:1 or at least 3:1and may be at most 30:1 or at most 25:1 or at most 20:1 or at most 15:1or at most 10:1 or at most 5:1 or at most 3:1 or at most 2:1. Further,the above description of temperature and pressure in extraction step a)also applies to the above-mentioned additional (extraction) step. Incase the present process comprises the above-mentioned additional step,the first solvent stream in extraction step a) may comprise demixingsolvent b) in addition to extraction solvent a) in which case the bottomstream from the first extraction column additionally comprises demixingsolvent b).

In the above-mentioned additional step wherein washing solvent c) isadded, it is preferred that the stream comprising washing solvent c) tobe added comprises no or substantially no heteroatom containing organiccompounds originating from the liquid hydrocarbon feedstock stream. Thispreference applies especially in a case where said stream is fed to thesecond extraction column at a relatively high position, as describedabove, where these heteroatom containing organic compounds couldre-contaminate the raffinate (top) stream. Advantageously, in thepresent invention, at least part of the first stream resulting from stepc) and comprising demixing solvent b) and optionally washing solvent c),and in case sorption step (ii) is performed in the present process, atleast part of the treated stream resulting from sorption step (ii),which streams may contain no or substantially no heteroatom containingorganic compounds originating from the liquid hydrocarbon feedstockstream, may be used as such washing solvent c) stream for feeding(recycling) to said additional step, especially in case demixing solventb) is identical to washing solvent c), especially water.

Further, at least part of the second stream comprising washing solventc) and extraction solvent a) resulting from the above-mentionedadditional (extraction) step may be fed to step b) to provide for atleast part of the demixing solvent b) that needs to be added in step b),especially in case demixing solvent b) is identical to washing solventc). Thus, advantageously, such washing solvent c) may function both asan extraction solvent extracting residual extraction solvent a) in saidadditional step and as a so-called “demixer” (or “antisolvent”) in stepb), i.e. as demixing solvent b), as further discussed above.

In case a washing solvent other than water is fed to an extractioncolumn for extracting extraction solvent a) used in step a), either inthe above-mentioned additional step or in step a) itself as describedabove, it may be preferred that in addition to such other solvent, wateris fed to the extraction column at a position which is higher than theposition at which that other solvent is fed. In this way,advantageously, the water fed at the higher position may extract anywashing solvent other than water away thereby preventing such otherwashing solvent from entering the (final) raffinate stream.Alternatively, the latter raffinate stream may be washed with water in aseparate step.

Upstream and Downstream Integration

In the present invention, the liquid hydrocarbon feedstock stream maycomprise at least part of a hydrocarbon product formed in a processcomprising cracking of plastics, preferably waste plastics, morepreferably mixed waste plastics, wherein at least part of the plasticscomprises heteroatom containing organic compounds.

Accordingly, the present invention also relates to a process for therecovery of aliphatic hydrocarbons from plastics, wherein at least partof the plastics comprises heteroatom containing organic compounds, saidprocess comprising the steps of:

(I) cracking the plastics and recovering a hydrocarbon productcomprising aliphatic hydrocarbons, heteroatom containing organiccompounds and optionally aromatic hydrocarbons; and

(II) subjecting a liquid hydrocarbon feedstock stream, which comprisesat least part of the hydrocarbon product obtained in step (I), to theabove-described process for the recovery of aliphatic hydrocarbons froma liquid hydrocarbon feedstock stream.

The preferences and embodiments as described above with reference to thepresent aliphatic hydrocarbons recovery process as such also apply tostep (II) of the present process for the recovery of aliphatichydrocarbons from plastics. In above-mentioned step (I), the resultinghydrocarbon product may be either a liquid or a solid or wax. In thelatter case, the solid or wax is first heated to make it liquid, beforesubjecting it to the aliphatic hydrocarbons recovery process in step(II).

In the above-mentioned process, at least part of the plastics as fed tostep (I) comprises heteroatom containing organic compounds, whichplastics are preferably waste plastics, more preferably mixed wasteplastics. In said step (I), the cracking of the plastics may involve athermal cracking process and/or a catalytic cracking process. Thecracking temperature in step (I) may be of from 300 to 800° C., suitablyof from 400 to 800° C., more suitably of from 400 to 700° C., moresuitably of from 500 to 600° C. Further, any pressure may be applied,which pressure may be sub-atmospheric, atmospheric or super-atmospheric.Heat treatment in step (I) causes melting of the plastics and crackingof its molecules into smaller molecules. The cracking in step (I) may becarried out as pyrolysis or as liquefaction. Both in pyrolysis and inliquefaction a continuous liquid phase is formed. In addition, inpyrolysis a discontinuous gas phase is formed that escapes the liquidphase and segregates into a continuous gas phase. In liquefaction, thereis no significant gas phase by applying a relatively high pressure.

Further, in step (I), subsequent condensation of a gas phase and/orcooling of a liquid phase provides a hydrocarbon product, which may beeither a liquid or a solid or wax, comprising aliphatic hydrocarbons,heteroatom containing organic compounds and optionally aromatichydrocarbons, at least part of which is subjected to the above-describedaliphatic hydrocarbons recovery process in step (II).

Above-described step (I) may be carried out in any known way, forexample in a way as disclosed in above-mentioned WO2018069794 and inWO2017168165, the disclosures of which are herein incorporated byreference.

Advantageously, aliphatic hydrocarbons as recovered in one of theabove-described processes for the recovery of aliphatic hydrocarbons,which may comprise varying amounts of aliphatic hydrocarbons within awide boiling point range, may be fed to a steam cracker without afurther pre-treatment, such as treatment with hydrogen (hydrotreating orhydroprocessing) as disclosed in above-mentioned WO2018069794. Inaddition to being used as a feed to a steam cracker, said recoveredaliphatic hydrocarbons may also advantageously be fed to other refiningprocesses including hydrocracking, isomerization, hydrotreating, thermalcatalytic cracking and fluid catalytic cracking. Further, in addition tobeing used as a feed to a steam cracker, said recovered aliphatichydrocarbons may also advantageously be separated into differentfractions which each may find a different application, such as diesel,marine fuel, solvent, etc.

Accordingly, the present invention also relates to a process for steamcracking a hydrocarbon feed, wherein the hydrocarbon feed comprisesaliphatic hydrocarbons as recovered in one of the above-describedprocesses for the recovery of aliphatic hydrocarbons. Further,accordingly, the present invention also relates to a process for steamcracking a hydrocarbon feed, comprising the steps of: recoveringaliphatic hydrocarbons from a liquid hydrocarbon feedstock stream in oneof the above-described processes for the recovery of aliphatichydrocarbons; and steam cracking a hydrocarbon feed which comprisesaliphatic hydrocarbons as recovered in the preceding step. In thepresent specification, said phrase “steam cracking a hydrocarbon feedwhich comprises aliphatic hydrocarbons as recovered in the precedingstep” may mean “steam cracking a hydrocarbon feed which comprises atleast part of the recovered aliphatic hydrocarbons”. The hydrocarbonfeed to the steam cracking process may also comprise hydrocarbons fromanother source, other than the present processes for the recovery ofaliphatic hydrocarbons. Such other source may be naphtha, hydrowax or acombination thereof.

Advantageously, in a case wherein the liquid hydrocarbon feedstockstream comprises aromatic hydrocarbons, especially polycyclic aromatics,heteroatom containing organic compounds, conjugated aliphatic compoundshaving two or more carbon-carbon double bonds, or a combination thereof,these have already been removed by the present aliphatic hydrocarbonsrecovery process as described above before feeding recoveredhydrocarbons to a steam cracking process. This is particularlyadvantageous in that said removed compounds, especially polycyclicaromatics, can no longer cause fouling in the preheat, convection andradiant sections of a steam cracker and in the downstream heat exchangeand/or separation equipment for a steam cracker, for example in transferline exchangers (TLEs) which are used to rapidly cool the effluent froma steam cracker. When hydrocarbons condense, they may thermallydecompose into a coke layer which may cause fouling. Such fouling is amajor factor determining the run length of the cracker. Reducing theamount of fouling results in longer run times without maintenanceshutdowns, and improved heat transfer in the exchangers.

The steam cracking may be performed in any known way. The hydrocarbonfeed is typically preheated. The feed can be heated using heatexchangers, a furnace or any other combination of heat transfer and/orheating devices. The feed is steam cracked in a cracking zone undercracking conditions to produce at least olefins (including ethylene) andhydrogen. The cracking zone may comprise any cracking system known inthe art that is suitable for cracking the feed. The cracking zone maycomprise one or more furnaces, each dedicated for a specific feed orfraction of the feed.

The cracking is performed at elevated temperatures, preferably in therange of from 650 to 1000° C., more preferably of from 700 to 900° C.,most preferably of from 750 to 850° C. Steam is usually added to thecracking zone, acting as a diluent to reduce the hydrocarbon partialpressure and thereby enhance the olefin yield. Steam also reduces theformation and deposition of carbonaceous material or coke in thecracking zone. The cracking occurs in the absence of oxygen. Theresidence time at the cracking conditions is very short, typically inthe order of milliseconds.

From the cracker, a cracker effluent is obtained that may comprisearomatics (as produced in the steam cracking process), olefins,hydrogen, water, carbon dioxide and other hydrocarbon compounds. Thespecific products obtained depend on the composition of the feed, thehydrocarbon-to-steam ratio, and the cracking temperature and furnaceresidence time. The cracked products from the steam cracker are thenpassed through one or more heat exchangers, often referred to as TLEs(“transfer line exchangers”), to rapidly reduce the temperature of thecracked products. The TLEs preferably cool the cracked products to atemperature in the range of from 400 to 550° C.

FIGURES

The present process for the recovery of aliphatic hydrocarbons from aliquid hydrocarbon feedstock stream is further illustrated by FIGS. 1and 2 .

In the process of FIG. 1 , a liquid hydrocarbon feedstock stream 1,which comprises aliphatic hydrocarbons (including conjugated aliphaticcompounds having two or more carbon-carbon double bonds, which arehereinafter referred to as “dienes”), aromatic hydrocarbons andheteroatom containing organic compounds; a first solvent stream 2 whichcomprises an organic solvent (for example N-methylpyrrolidone) which isan extraction solvent a) in accordance with the present invention; and asecond solvent stream 3 which comprises water which is an optionalwashing solvent c) in accordance with the present invention, are fed toan extraction column 4. In column 4, liquid hydrocarbon feedstock stream1 is contacted with first solvent stream 2 (organic solvent), therebyrecovering aliphatic hydrocarbons by liquid-liquid extraction of dienes,aromatic hydrocarbons and heteroatom containing organic compounds withthe organic solvent. Further, the water in second solvent stream 3removes organic solvent from the upper part of column 4 by liquid-liquidextraction of organic solvent with water. A stream 5 comprisingrecovered aliphatic hydrocarbons exits column 4 at the top. Further, astream 6 comprising organic solvent, water, dienes, aromatichydrocarbons and heteroatom containing organic compounds exits column 4at the bottom. Stream 6 and a stream 14 comprising additional water,which is a demixing solvent b) in accordance with the present invention,are combined, are combined, and the combined stream is fed to a decanter13. In decanter 13, the combined stream is separated into a stream 15comprising dienes, aromatic hydrocarbons and heteroatom containingorganic compounds and a stream 16 comprising organic solvent, water,dienes, aromatic hydrocarbons and heteroatom containing organiccompounds.

Further, in the process of FIG. 1 , stream 16 may be fed to a sorptionunit 10 containing a sorption agent removing dienes, aromatichydrocarbons and heteroatom containing organic compounds. Treated stream11 from sorption unit 10 comprises organic solvent and water. Stream 16or treated stream 11 is fed to a distillation column 7, where it isseparated into a top stream 8 comprising water and a bottom stream 9comprising organic solvent. In a case where stream 16 is fed todistillation column 7, top stream 8 additionally comprises dienes,aromatic hydrocarbons and heteroatom containing organic compounds and isfed to a sorption unit 12 containing a sorption agent removing dienes,aromatic hydrocarbons and heteroatom containing organic compounds.Treated stream 17 from sorption unit 12 comprises water, part of whichwater stream (stream 17 a) is sent back to distillation column 7 as areflux stream whereas the other part (stream 17 b) may be recycled viawater stream 14 and/or water stream 3. In a case where treated stream 11is fed to distillation column 7, top stream 8 may be fed to sorptionunit 12. If in the latter case, top stream 8 is not fed to sorption unit12, part of top stream 8 (stream 17 a) is sent back to distillationcolumn 7 as a reflux stream whereas the other part (stream 17 b) may berecycled via water stream 14 and/or water stream 3. Organic solvent frombottom stream 9 is recycled via organic solvent stream 2.

In the process of FIG. 2 , a liquid hydrocarbon feedstock stream 1,which comprises aliphatic hydrocarbons (including conjugated aliphaticcompounds having two or more carbon-carbon double bonds, which arehereinafter referred to as “dienes”), aromatic hydrocarbons andheteroatom containing organic compounds; and a first solvent stream 2which comprises an organic solvent (for example N-methylpyrrolidone)which is an extraction solvent a) in accordance with the presentinvention, are fed to a first extraction column 4 a. In column 4 a,liquid hydrocarbon feedstock stream 1 is contacted with first solventstream 2 (organic solvent), thereby recovering aliphatic hydrocarbons byliquid-liquid extraction of dienes, aromatic hydrocarbons and heteroatomcontaining organic compounds with the organic solvent, resulting in atop stream 5 a comprising recovered aliphatic hydrocarbons and organicsolvent and a bottom stream 6 comprising organic solvent, dienes,aromatic hydrocarbons and heteroatom containing organic compounds.Stream 5 a and a second solvent stream 3 which comprises water, which isan optional washing solvent c) in accordance with the present invention,are fed to a second extraction column 4 b. In column 4 b, stream 5 a iscontacted with second solvent stream 3 (water), thereby removing organicsolvent by liquid-liquid extraction of organic solvent with water. Astream 5 b comprising recovered aliphatic hydrocarbons exits column 4 bat the top. Further, a stream 14 comprising organic solvent and water,which water is a demixing solvent b) in accordance with the presentinvention, exits column 4 b at the bottom. Streams 6 and 14 arecombined, and the combined stream is fed to a decanter 13. In respect ofthe treatment in decanter 13 and further, downstream treatments in theprocess of FIG. 2 reference is made to the above description of thecorresponding treatments in the process of FIG. 1 .

1. A process for the recovery of aliphatic hydrocarbons from a liquidhydrocarbon feedstock stream comprising aliphatic hydrocarbons,heteroatom containing organic compounds and optionally aromatichydrocarbons, said process comprising the steps of: a) contacting atleast part of the liquid hydrocarbon feedstock stream with an extractionsolvent a) which contains one or more heteroatoms and subjecting theliquid hydrocarbon feedstock stream to liquid-liquid extraction with theextraction solvent a), resulting in a first stream comprising aliphatichydrocarbons and a second stream comprising extraction solvent a),heteroatom containing organic compounds and optionally aromatichydrocarbons; b) mixing at least part of the second stream resultingfrom step a) with a demixing solvent b) which contains one or moreheteroatoms and has a miscibility in heptane which is lower than themiscibility of extraction solvent a) in heptane, and separating theresulting mixture into a first stream comprising heteroatom containingorganic compounds and optionally aromatic hydrocarbons and a secondstream comprising extraction solvent a), demixing solvent b), heteroatomcontaining organic compounds and optionally aromatic hydrocarbons; c)separating at least part of the second stream resulting from step b)into a first stream comprising demixing solvent b), optionallyheteroatom containing organic compounds and optionally aromatichydrocarbons and a second stream comprising extraction solvent a); d)recycling at least part of the extraction solvent a) from the secondstream resulting from step c) to step a); and e) optionally recycling atleast part of the demixing solvent b) from the first stream resultingfrom step c) to step b), wherein: (i) before step c), heteroatomcontaining organic compounds and optionally aromatic hydrocarbons areremoved from the second stream resulting from step b) by contacting atleast part of that stream with a sorption agent; and/or (ii) after stepc), heteroatom containing organic compounds and optionally aromatichydrocarbons are removed from the first stream resulting from step c),wherein that stream comprises demixing solvent b), heteroatom containingorganic compounds and optionally aromatic hydrocarbons, by contacting atleast part of that stream with a sorption agent.
 2. The processaccording to claim 1, wherein step c) comprises: separating at leastpart of the second stream resulting from step b) by distillation into atop stream comprising demixing solvent b), optionally heteroatomcontaining organic compounds and optionally aromatic hydrocarbons and abottom stream comprising extraction solvent a), and wherein: (i)heteroatom containing organic compounds and optionally aromatichydrocarbons are removed from the second stream resulting from step b)by contacting at least part of that stream with a sorption agent, and atleast part of the treated stream resulting from step (i) is fed to stepc); and/or (ii) the top stream resulting from step c) comprises demixingsolvent b), heteroatom containing organic compounds and optionallyaromatic hydrocarbons, and heteroatom containing organic compounds andoptionally aromatic hydrocarbons are removed from that stream bycontacting at least part of that stream with a sorption agent.
 3. Theprocess according to claim 1, wherein: the extraction solvent a) has aR_(a,heptane) of at least 5 MPa1/2, and the demixing solvent b) has aR_(a,heptane) of at least 20 MPa1/2, wherein R_(a,heptane) refers to theHansen solubility parameter distance with respect to heptane asdetermined at 25° C.; and the R_(a,heptane) for the demixing solvent b)is greater than the R_(a,heptane) for extraction solvent a), whereinsaid difference in R_(a,heptane) for solvents a) and b) is at least 1MPa1/2.
 4. The process according to claim 1, wherein the extractionsolvent a) comprises one or more solvents selected from the groupconsisting of ammonia diols and triols, including monoethylene glycol(MEG), monopropylene glycol (MPG), any isomer of butanediol andglycerol; glycol ethers, including oligoethylene glycols, includingdiethylene glycol, triethylene glycol and tetraethylene glycol, andmonoalkyl ethers thereof, including diethylene glycol ethyl ether;amides, including N-alkylpyrrolidone, wherein the alkyl group maycontain 1 to 8 or 1 to 3 carbon atoms, including N-methylpyrrolidone(NMP), formamide and di- and monoalkyl formamides and acetamides,wherein the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms,including dimethyl formamide (DMF), methyl formamide and dimethylacetamide; dialkylsulfoxide, wherein the alkyl group may contain 1 to 8or 1 to 3 carbon atoms, including dimethylsulfoxide (DMSO); sulfones,including sulfolane; N-formyl morpholine (NFM); furan ring containingcomponents and derivatives thereof, including furfural, 2-methyl-furan,furfuryl alcohol and tetrahydrofurfuryl alcohol; hydroxy esters,including lactates, including methyl and ethyl lactate; trialkylphosphates, including triethyl phosphate; phenolic compounds, includingphenol and guaiacol; benzyl alcoholic compounds, including benzylalcohol; aminic compounds, including ethylenediamine, monoethanolamine,diethanolamine and triethanolamine; nitrile compounds, includingacetonitrile and propionitrile; trioxane compounds, including1,3,5-trioxane; carbonate compounds, including propylene carbonate andglycerol carbonate; and cycloalkanone compounds, includingdihydrolevoglucosenone.
 5. The process according to claim 1, wherein thedemixing solvent b) comprises one or more solvents selected from thegroup consisting of water and one or more organic solvents selected fromthe group consisting of diols and triols, including monoethylene glycol(MEG), monopropylene glycol (MPG), any isomer of butanediol andglycerol; glycol ethers, including oligoethylene glycols, includingdiethylene glycol, triethylene glycol and tetraethylene glycol, andmonoalkyl ethers thereof, including diethylene glycol ethyl ether;amides, including N-alkylpyrrolidone, wherein the alkyl group maycontain 1 to 8 or 1 to 3 carbon atoms, including N-methylpyrrolidone(NMP), formamide and di- and monoalkyl formamides and acetamides,wherein the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms,including dimethyl formamide (DMF), methyl formamide and dimethylacetamide; dialkylsulfoxide, wherein the alkyl group may contain 1 to 8or 1 to 3 carbon atoms, including dimethylsulfoxide (DMSO); sulfones,including sulfolane; N-formyl morpholine (NFM); furan ring containingcomponents and derivatives thereof, including furfural, 2-methyl-furan,furfuryl alcohol and tetrahydrofurfuryl alcohol; hydroxy esters,including lactates, including methyl and ethyl lactate; trialkylphosphates, including triethyl phosphate; phenolic compounds, includingphenol and guaiacol; benzyl alcoholic compounds, including benzylalcohol; aminic compounds, including ethylenediamine, monoethanolamine,diethanolamine and triethanolamine; nitrile compounds, includingacetonitrile and propionitrile; trioxane compounds, including1,3,5-trioxane; carbonate compounds, including propylene carbonate andglycerol carbonate; and cycloalkanone compounds, includingdihydrolevoglucosenoneas.
 6. The process according to claim 1, wherein:a washing solvent c) is added to step a) resulting in a first streamcomprising aliphatic hydrocarbons and a second stream comprising washingsolvent c), extraction solvent a), heteroatom containing organiccompounds and optionally aromatic hydrocarbons; or the first streamresulting from step a) comprises aliphatic hydrocarbons and extractionsolvent a), at least part of which first stream is contacted with awashing solvent c) and is subjected to liquid-liquid extraction with thewashing solvent c), resulting in a first stream comprising aliphatichydrocarbons and a second stream comprising washing solvent c) andextraction solvent a).
 7. The process according to claim 6, wherein thewashing solvent c) is identical to or different from demixing solventb).
 8. A process for the recovery of aliphatic hydrocarbons fromplastics, wherein at least part of the plastics comprises heteroatomcontaining organic compounds, said process comprising the steps of: (I)cracking the plastics and recovering a hydrocarbon product comprisingaliphatic hydrocarbons, heteroatom containing organic compounds andoptionally aromatic hydrocarbons; and (II) subjecting a liquidhydrocarbon feedstock stream, which comprises at least part of thehydrocarbon product obtained in step (I), to the process of claim
 1. 9.Process for steam cracking a hydrocarbon feed, wherein the hydrocarbonfeed comprises aliphatic hydrocarbons as recovered in a processaccording to claim
 1. 10. Process for steam cracking a hydrocarbon feed,comprising the steps of: recovering aliphatic hydrocarbons from a liquidhydrocarbon feedstock stream in a process according to claim 1; andsteam cracking a hydrocarbon feed which comprises aliphatic hydrocarbonsas recovered in the preceding step.